In fluid or gas handling systems in industry, particularly pressurised systems, it is known to provide a so-called closure assembly to provide quick and secure access into some part of the interior of the fluid or gas handling system. For example, in the gas, chemical and waste treatment industries, it is common for there to be various pipelines and vessels that generally operate in a pressurised environment. Such vessels need to be openable for loading/unloading and also for servicing operations such as cleaning, inspection, changing filters or other replacable elements.
Some applications of closure apparatus include those in the petrochemical, pharmaceutical, and chemical process industries, such as blow downs, manways, filters, strainers, coalescers, waste disposal vessels and autoclaves. Typically, closures may operate with working pressures up to 5×106 Pa and temperatures from minus 50° F. to 400° F.
Many types of locking apparatus can be provided for locking a closure in the closed position. For example, there may be a flange around the opening. A covering or closing element which forms a cap may be provided: It may be engageable with the opening by a screw thread or other suitable apparatus.
The opening, and the corresponding closure, may be any suitable size. For example, closures may be as small as 100 mm. However, in many applications, very large closures are required, for example for large pressure vessels. For example, it may be necessary to have a closure capable of closing an opening of diameter greater than 1000 mm and may be as much as 1500 mm. Particularly where the operating pressures are particularly high, the closure may accordingly be very large and heavy.
Problems may be encountered when the closure is very large, for example when it has a diameter of 1000 mm or more. In particular, the closure may be very heavy and difficult to manipulate or rotate in the unlocking operation. Further, where the closure is of very large diameter, and locking is provided by locking lugs, in order to obtain a strong locking force around the periphery of the closure, a large number of lugs may be required which are difficult to operate together. This may also make the locking system very expensive to manufacture.
It is an object of the present invention to provide a closure apparatus which overcomes the problems of the prior art. It is a further object of the present invention to provide a method of closing an opening using the closure apparatus, which overcomes the problems of the prior art.